It has indeed crossed my mind (and that of some of the people I've been
talking with) that one may want to have a simple "closure" - i.e.,
something much simpler than what most non-monotonic formalisms provide.
It seems, though, that some of the things you describe below can be
achieved by the autoepistemic K operator [1,2], by DL-safe variables
[3,4], or the approach proposed in [5]. In any case, it needs spelling
out explicitly...
Best Regards,
Pascal.
[1] http://portal.acm.org/citation.cfm?doid=1754399.1754403
[2]
http://knoesis.wright.edu/faculty/pascal/resources/publications/mknftheo.pdf
[3]
http://knoesis.wright.edu/faculty/pascal/resources/publications/ELP_iswc08.pdf
[4] http://korrekt.org/page/Description_Logic_Rules_%28monograph%29
[5] http://knoesis.wright.edu/faculty/pascal/resources/publications/ELP2.pdf
On 11/16/2010 12:52 PM, DJA222 wrote:
> Dear OWL Staff,
>
> Hereby I would like to suggest an elegant solution to let OWL/RDF
> cover Closed World Assumptions (CWA), incl Unique Name Assumption
> (UNA).
>
> Due to its Open World Assumption (OWA), OWL/RDF can hardly be used
> for e.g.: 1. finding (:instantiating) pre-defined individuals with a
> certain number of properties or without these properties at all (e.g.
> cardinality 0). 2. validation. OWL/RDF's OWA asserts that everything
> is possible (->infinite) until asserted otherwise by constraints
> (->finite). But doesn't infinity envelopes finity? Isn't processing
> things in a finite world (CWA) just a valid part of the infinite
> world (OWA)? Finite means that things are or (immidiately) can be
> made explicit. Then why not simply introduce a term like
> e.g."Explicit" that can be added to every constraint and applies to
> things/values that are visible at the very moment of instantiation?
>
> Example class expression: Person and (hasChild exactly 0 Explicit) :
> at the very moment that this class is being instantiated it "scans"
> for (pre-definied) individuals in class Person for which the property
> "hasChild" is explicitly absent (:exactly 0 Explicit). Although
> OWL/RDF itself leaves open the possibility that the individuals still
> might have hidden "hasChild" properties, the reasoner just looks for
> explicitly absent properties because the class expression tells it to
> do so.
>
> This way it can also be used for validation/integrity-check with a
> class expression with "Explicit" included: if something is asserted,
> that can't be derived from explicitly present assertions at the very
> moment of instantiation, than this will be reported: NOT as being a
> OWL/RDF error/conflict/inconsistency, but just as a note to the user
> who fabricated this class expression. Again, without OWL/RDF itself
> denying that there might still be assertions that are just not
> visible at the moment of instantiation.
>
> Same story for UNA: by adding a term like e.g. "Unique" in a class
> expression it might notify the user (who wrote the expression) upon
> instantiation, that it has found individuals who are asserted
> (directly or implied) to be identical but have different names or
> that it has found more individuals than expected. Again, without
> OWL/RDF itself denying that there might by assertions that are just
> not visible at the moment of instantiation.
>
> All above OWL/RDF examples would still comply with OWA and Non-UNA
> demands, by assuming the possible outcome (with the terms "Explicit"
> and "Unique" used in expressions) not as OWL/RDF conlicts, but just
> as (user) notifications.
>
> Above is extremely important in research where INDIVIDUALS and
> relations between them are at the focus, instead of the more generic
> class approach. In certain researches, thousands and thousands of
> data snippets (:Individuals) come in from different places and you
> want to look for certain properties/relations that these pieces
> share/have with/to one another. This can not easily be automated with
> present OWL/RDF. Yes, one might use SPARQL in some ways, but the aim
> is to let simple class instantiation do its work.
>
> In my conviction, with a slight addition, OWL/RDF semantics can proof
> to be a more complete basis for ANY semantic real world application
> and solution, and not just for a limited part!
>
> Hopefully you might reconsider this idea, or find find some similar
> solution, that really is in the need of many (potential) OWL/RDF
> practitioners.
>
> Sincerely yours,
>
> DJ Alexander
--
Prof. Dr. Pascal Hitzler
Dept. of Computer Science, Wright State University, Dayton, OH
pascal@pascal-hitzler.de http://www.knoesis.org/pascal/
Semantic Web Textbook: http://www.semantic-web-book.org
Semantic Web Journal: http://www.semantic-web-journal.net